*Excludes Observations that spanned multiple years

  B
b
t
W
w
 
Pre 1970000000
1970000000
1971000000
1972000000
1973000000
1974000000
1975000000
1976000000
1977000000
1978000000
1979000000
1980000000
1981000101
1982000000
1983000000
1984000000
1985000000
1986000000
1987000707
1988000516
1989000415
1990000156
1991002057
1992001326
199300011819
199400075865
199500026062
199600036669
199700023335
199800001717
199900011112
200000014445
200100051823
200200021719
200300031821
200400013031
200500031922
200600051520
200700052429
200800026668
2009000404
201000091322
20110005611
2012000077
201300014041
201400002424
2015000606
2016000112
2017000000
2018000000
Total00390619712